The subject of the present invention is an iridescent composition for topical application, comprising at least one water-soluble surfactant and an aqueous dispersion of particles of polymer, the said particles having a mean size in numerical terms ranging from about 50 to 300 nm. The quantity of particles of polymer being at least 3% by weight of active material relative to the total weight of the composition.The composition according to the invention has a very attractive visual appearance by virtue of its iridescent color.The invention also relates to the uses of the composition of the invention in the cosmetic field, in particularly for the treatment, protection, care, removal of make-up from and/or cleansing of the skin, the lips and/or the hair, and/or for the application of make-up to the skin and/or the lips.

Claim:

What is claimed is:

1. A method for cleansing the skin, said method comprising cleansing the skin of a human with a cosmetic composition comprising at least one water-soluble surfactant andmonodisperse particles of polymer in aqueous dispersion, said particles having a mean size of from 50 to 300 nm and the quantity of said particles is at least 3% by weight relative to the total weight of the composition, wherein said surfactant has anHLB equal to or greater than 11.

2. The method according to claim 1, wherein the dispersion and/or the composition exhibits a colorimetric difference ranging from 2 to 100.

3. The method according to claim 1, wherein the turbidity of the composition is greater than 100.

4. The method according to claim 1, wherein the viscosity of the composition is from 0.01 Pa.s to 10 Pa.s.

5. The method according to claim 1, wherein the surfactant is chosen from the group consisting of nomonic surfactants, anionic surfactants, zwitterionic surfactant, amphoteric surfactants and mixtures thereof.

10. The method according to claim 1, wherein the quantity of polymer particles is from 3 to 50% relative to the total weight of the composition.

11. The method according to claim 1, wherein the quantity of surfactant is from 0.5 to 50% by weight relative to the total weight of the composition.

12. The method according to claim 1, wherein the composition further comprises at least one active agent.

13. The method according to claim 1, further comprising 30 to 96.5% by weight of water relative to the total weight of the composition.

14. The method according to claim 1, further comprising one or more solvents chosen from the group consisting of alcohols comprising 1 to 8 carbon atoms, polyols, sugars and mixtures thereof.

15. The method according to claim 1, wherein the quantity of surfactant is from 2 to 40% by weight relative to the total weight of the composition.

16. The method according to claim 1, wherein the quantity of polymer particles is from 3.5 to 40% by weight relative to the total weight of the composition.

17. An iridescent composition for topical application comprising at least one water-soluble surfactant and monodisperse particles of polymer in aqueous dispersion, said particles having a mean size of from 50 to 300 nm and the quantity of saidparticles is at least 3% by weight relative to the total weight of the composition, wherein said surfactant has an HLB equal to or greater than 11, wherein the polymer particles are chosen from the group consisting of particles of acrylic acid/ethylacrylate copolymer, particles of styrene/butyl acrylate/methyl methacrylate/methacrylic acid hybrid copolymer, and mixtures thereof.

Description:

The subject of the invention is an iridescent compositionfor topical application, comprising at least one water-soluble surfactant and an aqueous dispersion of particles of polymer, the said particles having a mean size in numerical terms ranging from about 50 to 300 nm, and the uses of the said composition,in particular for the treatment, protection, care, removal of make-up from and/or cleansing of the skin, the lips and/or the hair, and/or as make-up for the skin and/or the lips.

Care and/or cleansing compositions for the skin are generally in the form of transparent or white products depending on their constituent ingredients. To make them more attractive, it is possible to colour them by adding various colouring agentsthereto. These colouring agents may be, for example, pigments such as lacquers, inorganic pigments or pearlescent pigments, or soluble colorants. However, the colours obtained are often unstable to light.

To obtain iridescent coloured effects, it is possible to use pearlescent pigments with a variety of colours. However, most often, the iridescent effect obtained with these pearlescent pigments is fairly weak, and, in addition, these pigments aredifficult to disperse and to maintain in suspension, in particular in cleansing compositions which are often quite fluid. The incorporation of such pigments is therefore delicate and the reproducibility of the effect obtained is not certain.

It has therefore been sought to design products having an iridescent effect without incorporating pearlescent pigments.

The Applicant has found, surprisingly, that the combination of polymers, in the form of particles in dispersion (in emulsion or in latex form), with surfactants, in particular anionic or nonionic surfactants, allows the production of productswith an iridescent appearance, which are very attractive for consumers without having the technical difficulties of suspension of the particles.

Indeed, compositions containing a colouring system, which is obtained from colloidal crystalline networks in the medium, giving an iridescent colour without the addition of pigments or colorants, are known from the document WO-00/47167. However,to obtain such an effect, the medium has to have a relatively low ionic strength and a conductance (the conductance is the product of the conductivity of the composition times the measuring cell constant) of less than 2.5 .mu..OMEGA..sup.-1, which limitsthe addition of ionic additives such as ionic surfactants and certain active agents. However, in cosmetic compositions and in particular in cleansing compositions, it is often necessary to introduce ionic compounds into the medium. In addition, it maybe advantageous to introduce surfactants into a composition, for example, to solubilize therein perfumes and active agents, or as agents for removing make-up from the skin.

The need therefore remains for an iridescent composition which can retain this iridescent character regardless of the conductance and the ionic strength of its constituent medium.

The Applicant has found, surprisingly, that the disadvantages of the prior art could be remedied using at least 3% by weight of active material of an aqueous dispersion of monodisperse particles of polymer, having a mean particle size innumerical terms ranging from about 50 to 300 nm, and combining water-soluble surfactants therewith.

Accordingly, the subject of the present invention is an iridescent composition for topical application comprising at least one water-soluble surfactant and monodisperse particles of polymer in aqueous dispersion, the said particles having a meansize in numerical terms ranging from 50 to 300 nm and the quantity of the said particles being at least 3% by weight of active material relative to the total weight of the composition.

"Mean size in numerical terms" refers to the mean diameter in numerical terms of the preferably spherical particles of polymer of the dispersion, this size being the original size of the particles before they are mixed with other constituents. Indeed, the size of the particles may be different before and after their incorporation into a composition, because, as described below, the particles may consist of polymer comprising a monomer which is soluble or which swells in alkaline media, suchthat the particles of polymer may swell in water or alkaline media after incorporation into the composition for topical application.

The size of the particles is measured by means of the Brookhaven 90Plus particle size analyser. The measurements are carried out at 90.degree..

Moreover, the quantity of particles in the present application is indicated by weight of active material, that is to say by weight of dry matter content of particles of polymers.

The composition of the invention is characterized by its iridescent effect and it has the advantage of having this iridescent effect, regardless of the value of its conductance (expressed in ohm.sup.-1 or in Siemens).

Macroscopically, the iridescent effect results in variations in colour which are perceived by an observer who would be moving around the surface of the product illuminated by a fixed light beam. By contrast, a product is not iridescent when theobserver does not see a change in colour during their movement.

The iridescent effect may be measured by means of a goniometer, the principle of which is to measure the colour by varying the geometric conditions of observations (angles of illumination and of detection of the reflected light). The method ofmeasurement used here and described in greater detail below is inspired by that described in "Color effects from thin film designs" by Roger Phillips, Mike Nofi and Robert Slusser (Flex Products Inc 2793 Nothpoint Parkway Santa Rosa Calif. 95407).

Method of Measurement:

The samples, at the temperature of 23.degree. C., fill a vessel 5 mm in height. Their top surface is placed in the plane of measurement of a spectrophotogoniometer. The spectra are measured as a reflexion at 400-760 nm in steps of 5 nm. Thespectra are recorded at an angle of illumination set at 55.degree. and at angles of detection placed successively at the following values: 90.degree. (scattering), 100, 110, 120, 130 and 140.degree.. This path simulates the variations perceived by anobserver who would be moving around the surface of the product illuminated by a fixed light beam.

The different spectra thus obtained are processed in order to obtain the calorimetric parameters L*a*b* in the CIELAB space (reference: ceramic bore MINOLTA Number 20231050 at the illumination D65 Y=94.1, x=0.3157, y=0.3331). The colour path isobtained by joining in the plane of abscissa a* and of ordinate b*, the coordinates of the colorimetric values calculated. a* varies from green to red and b* varies from blue to yellow. When a* is negative, the colour possesses a dominant green; whenit is positive, the colour possesses a dominant red. When b* is negative, the colour possesses a dominant blue; when it is positive, the colour possesses a dominant yellow. The calorimetric difference is equal to the square root of the sum of thesquares of the differences in the values a and b relative to the first measurement (detection angle of 90 degrees, a measurement close to that obtained with a conventional colorimeter such as the chromameter MINOLTA CR300).

Thus, a composition has an iridescent appearance when the colorimetric difference for this composition or for the dispersion of particles of polymer which it contains is greater than 2, and preferably varies from 2 to 100, preferably from 3 to 60for an angle of illumination of 55.degree. and an angle of detection of between 100 and 140.degree. as described above. The incident light is characterized by a beam having a diameter of 8 mm, an angular resolution of 1.3 degrees, a wavelength of 250to 800 nm and a 1 nm type resolution.

A product which does not possess an iridescent effect is characterized, for example, by differences varying from 0.1 to 1 under the same measurement conditions.

The composition of the invention is also characterized by its turbidity, that is to say its opacity. The turbidity measures the opacity of a product. The NTU (Nephelometric Turbidity Units) are the units of measurement of the turbidity of acomposition. The measurement of turbidity may be carried out, for example, with a turbidimeter model 2100P from the company HACH, the tubes used for the measurement being identified by the references AR397A cat 24347-06. The measurements are carriedout at room temperature (20.degree. C. to 25.degree. C.). The higher the turbidity, the greater the opacity of the product. The composition of the invention is generally translucent to opaque and it preferably has a turbidity greater than 100.

Moreover, the composition according to the invention generally has a viscosity ranging from 0.1 poise to 100 poises (0.01 Pa.s to 10 Pa.s), preferably from 4 to 70 poises (0.4 to 7 Pa.s) and more preferably from 5 to 30 poises (0.5 to 3 Pa.s),this viscosity being measured at about 25.degree. C. with a Rheomat 180 apparatus using a 2, 3, 4 or 5 rotor depending on the viscosity range, at 200 s.sup.-1.

The composition of the invention is a composition for topical, and in particular cosmetic, use, and, as such, it contains a physiologically acceptable medium, that is to say a medium compatible with the skin, the hair, the nails and/or the mucousmembranes (lips). In addition, it preferably has a pH compatible with the skin, that is to say preferably ranging from 3 to 8 and, even better, from 5 to 7. This pH value may depend on the type of polymer used.

The polymer particles used in the composition of the invention should be monodisperse, that is to say that the results of measurements of the diameter of the particles are statistically distributed around a mean and according to a single Gaussiancurve. The variation relative to the mean should not exceed 10% per 100% of particles. This means that the particles practically all have the same size. This size ranges from 50 to 300 nm, preferably from 90 to 230 nm and even better from 100 to 200nm. The size of the particles is measured by means of the Brookhaven 90Plus particle size analyser. The measurements are carried out at 90.degree..

The particles consist of polymers. They become suspended or dispersed in water, in latex or emulsion form. Latexes are aqueous dispersions of particles of polymers, as described in "An introduction to polymer colloids" by F. CANDAU and R. H.OTTEWILL, Kluwer Academic Publishers, March 1989. The term polymer is understood here to mean both homopolymers obtained from a single type of monomer and copolymers obtained from several types (two or more) of monomers. These polymers may be eitherassociative polymers (that is to say possessing a hydrophobic part and a hydrophilic part) or nonassociative polymers (that is to say hydrophilic or water-soluble). They are dispersible in water and may exhibit swelling in alkaline media (oralkaline-swelling) or not. The polymers may be of any type: nonionic, anionic, cationic, zwitterionic or amphoteric.

The particles which can be used in the composition of the invention preferably consist of ionic polymers and even better anionic polymers. These polymers are dispersible in water and preferably exhibit alkaline-swelling. The preferred polymerspossess at least one monomer soluble in alkaline media, such as monomers of acrylic, methacrylic, vinylacetic, maleic, crotonic and itaconic acids. They may contain another monomer such as styrene, butadiene, ethylene, acrylonitrile, chloroprene,vinylidene chloride, isoprene, isobutylene, vinyl chloride, and esters of acrylic, methacrylic, vinylacetic, maleic, crotonic and itaconic acids and mixtures thereof.

Thus, the polymer particles may be chosen, for example, from the particles consisting of the following anionic polymers: 1) homopolymers of acrylic acid, such as those of the dispersions (in aqueous emulsion) marketed under the names MIRACARE XC96/36, MIRACARE XC 96/37 and MIRACARE XC 96/52 (acrylic nanolatex) by the company RHODIA CHIMIE. 2) copolymers of acrylic acid and of other monomers, such as those of the dispersions marketed under the names NEOCRYL PD-723-B (particle size: 114 nm),NEOCRYL XK 90 (particle size: 109 nm), NEOCRYL XK 53 (particle size: 96 nm) by the company AVECIA RESINS; ECOCRYL VS 301 (particle size: 150 nm) by the company ATOCHEM; NEOCRYL XK-75 (particle size: 102 nm) (aqueous emulsion of an acrylic acid/butylmethacrylate/methyl methacrylate/butyl acrylate copolymer) by the company AVECIA RESINS; MIRACARE XC 97-8 to 13 (acrylic/methyl methacrylate/butyl acrylate/methacrylic acid copolymer and derivatives in nonionic aqueous nanoemulsion) by the company RHODIACHIMIE, ACRYSOL 33 (or ACULYN 33) (acrylic acid/ethyl acrylate copolymer) (particle size: 110 nm) by the company ROHM & HMS. 3) styrene derivatives, such as those of the dispersions marketed under the name SETALUX 6801 AQ 24 (styrene/butylacrylate/methyl methacrylate/methacrylic acid hybrid copolymer) (particle size: 186 nm) by the company AKZO NOBEL; under the name RHODOPAS GS 125 (particle size: 170 nm) by the company RHONE POULENC, under the names NEOCRYL XK 61 (anionic acrylic/styrenecopolymer) (particle size: 76 nm), NEOCRYL A 1079 (styrene/acrylate copolymer) (particle size: 115 nm) by the company AVECIA RESINS; under the name RK-3-59A-PMN (mixture of two styrene/acrylic polymers (nucleus/envelope)) (particle size: 116 nm) by thecompany ROHM-HAAS, under the name DOW LATEX 432 (styrene/acrylate copolymer) (particle size: 145 nm) by the company LAMBERT-RIVIERE, under the name SCX 8060 (particle size: 116 nm) by the company JOHNSON POLYMER France. 4) fluorinated derivatives, suchas those of the dispersions marketed under the references LUMIFLON E-3029 (anionic aqueous dispersion containing 50% of hydroxylated fluorinated polymer) (particle size: 100 nm) and LUMIFLON FE-3000 (anionic aqueous dispersion containing 50% ofhydroxylated fluorinated polymer (particle size: 150 nm) by the company ASAHI GLASS. 5) silicone-based derivatives, such as that of the dispersion marketed under the reference HYCAR 26348 (acrylates/acrylonitrogen/siloxane copolymer) (particle size: 133nm) by the company GOODRICH. 6) diisocyanate derivatives, such as that of the dispersion marketed under the reference NEOPAC E-106 (urethane/acrylate copolymer (and) methylpyrrolidone (and) triethylamine) (particle size: 98 nm) by the company AVECIARESINS.

According to a preferred embodiment of the invention, particles of acrylic acid/ethyl acrylate copolymer, particles of styrene/butyl acrylate/methyl methacrylate/methacrylic acid hybrid copolymer, that is to say the dispersions sold under thenames ACRYSOL 33 or ACULYN 33 by the company ROHM & HAAS and SETALUX 6801 AQ 24 by the company AKZO NOBEL, and mixtures thereof are used. These dispersions are characterized by their colorimetric difference. When the polymer dispersion "ACULYN 33" isused, it is preferable that the composition has a pH value ranging from 3 to 6.3.

As shown in the table above, the particles of SYNTHALEN W2000 are not monodisperse, that is to say that their size is not homogeneous and comprises several Gaussian curves. The comparative results presented later show that this polymerdispersion is not appropriate for obtaining an iridescent effect, whereas the two dispersions "ACULYN 33" and "SETALUX 6801 AQ 24" which are monodisperse allow iridescent compositions to be obtained.

The quantity of particles of polymer in the composition of the invention depends on the polymer used. It may range, for example, from 3 to 50%, preferably from 3.5 to 40% and even better from 4 to 30% by weight (of active material or dry matter)relative to the total weight of the composition.

The composition according to the invention contains at least one water-soluble surfactant. The surfactant used may be chosen from nonionic, anionic, zwitterionic and amphoteric water-soluble surfactants and mixtures thereof. The expression"water-soluble surfactant" is understood to mean any surfactant soluble in water at room temperature (about 25.degree. C.). Such surfactants generally have an HLB (Hydrophilic Lipophilic Balance) value equal to or greater than 11.

The total quantity of surfactant(s) may range, for example, by weight of active material, from 0.5 to 50% by weight, preferably from 2 to 40% by weight and even better from 3 to 30% by weight relative to the total weight of the composition.

As surfactants which can be used in the composition of the invention, there may be mentioned for example:

i) Nonionic Surfactants

There may be used as nonionic surfactants, esters of polyols and of fatty acids, esters of polyethylene glycols and of fatty acid, derivatives of fatty alcohols and of polyols (ethers), and oxyalkylenated (oxyethylenated and/or oxypropylenated)derivatives of these compounds.

There may be used, for example, as amphoteric and zwitterionic surfactants, betaines, N-alkylamidobetaines and their derivatives, glycine derivatives, sultaines, alkyl polyaminocarboxylates, alkyl amphoacetates, and mixtures thereof.

It is also possible to use a mixture of two or more of these surfactants.

It is possible to choose in particular the surfactant from those indicated in the following list which is not exhaustive:

The physiologically acceptable medium of the composition of the invention comprises water. The quantity of water may range from 30 to 96.5%, preferably from 40 to 95% by weight relative to the total weight of the composition. It may contain, inaddition to water, one or more solvents chosen from lower alcohols comprising from 1 to 8 carbon atoms, such as ethanol; polyols such as glycerin; glycols such as butylene glycol, isoprene glycol, propylene glycol, polyethylene glycols such as PEG-8;sorbitol; sugars such as glucose, fructose, maltose, lactose, sucrose; and mixtures thereof. The quantity of solvent(s) in the composition of the invention may range from 0.5 to 30% by weight and preferably from 5 to 20% by weight relative to the totalweight of the composition.

The composition of the invention may also contain customary additives in the cosmetic field, such as mattifying inorganic or organic fillers, active agents, preservatives, gelling agents, plasticizers, antioxidants, perfumes, odour absorbers,antifoaming agents, sequestrants (EDTA), acidic or basic pH regulators, or buffers, pigments and pearlescent agents (in a quantity such that this does not disrupt the desired effect), polymers, fatty materials made compatible with the aqueous medium,such as oils or waxes, in so far as the additive does not impair the properties sought for the composition of the invention. The quantities of these various additives are those conventionally used in the fields considered, and for example from 0.01 to20% of the total weight of the composition.

As active agents, it is possible to incorporate any active agent normally used in the cosmetic and dermatological fields, such as water-soluble or fat-soluble vitamins or provitamins, for example vitamins A (retinol), C (ascorbic acid), B3 or PP(niacinamide), B5 (panthenol), E (tocopherol), K1, beta-carotene, and the derivatives of these vitamins and in particular their esters; hormones or derivatives such as DHEA and 7.alpha.-hydroxy DHEA; antiseptics; antiseborrhoeics; antimicrobials such asbenzoyl peroxide, salicylic acid, triclosan, azelaic acid, niacinamide (vit. PP); moisturizers such as glycerin, hyaluronic acid, pyrrolidonecarboxylic acid (PCA) and its salts, sodium pidolate, serine, xylitol, trehalose, ectoin, ceramides, urea;keratolytic and antiageing agents such as alpha-hydroxy acids such as glycolic acid, citric acid, lactic acid, beta-hydroxy acids such as salicylic acid, coenzyme Q10; sunscreens; optical brighteners; slimming agents such as caffeine, theophylline,theobromine, anti-inflammatory agents such as 18-.beta.-glycyrrhetinic acid and ursolic acid. It is also possible to use a mixture of two or more of these active agents. The active agent(s) may be, for example, present in a concentration ranging from0.01 to 20%, preferably from 0.1 to 10% and even better from 0.5 to 5% of the total weight of the composition.

The composition of the invention may be provided in any of the galenic forms normally used in the cosmetic and dermatological fields. It is generally provided in the form of a gel and is prepared according to the customary methods, that is tosay by mixing the surfactant and the polymer in the aqueous medium and adjusting the pH if necessary.

The composition according to the invention may comprise an oily phase (or fatty phase) comprising at least one oil, provided that it is solubilized in the medium, for example by forming a microemulsion. The oil(s) may be chosen from oils ofplant origin (jojoba, avocado, sesame, sunflower, maize, soyabean, safflower, grapeseed), mineral oils (petroleum jelly, hydrogenated or nonhydrogenated isoparaffins, isohexadecane, squalane), synthetic oils (parleam, isopropyl myristate, cetearyloctanoate, polyisobutylene, ethylhexyl palmitate, alkyl benzoates), volatile or nonvolatile silicone oils such as polydimethylsiloxanes (PDMS) and cyclodimethylsiloxanes or cyclomethicones, and fluorinated or fluorosilicone oils, as well as mixtures ofthese oils. The oily phase may contain, in addition, other fatty constituents such as fatty alcohols such as stearyl alcohol, cetyl alcohol and the mixture thereof (cetearyl alcohol); fatty acids; waxes; silicone gums. The oily phase may be present ina quantity ranging, for example, from 0.01 to 20% by weight relative to the total weight of the composition.

The composition according to the invention finds application in a large number of treatments, in particular cosmetic treatments, of the skin, including the scalp, the hair, the nails and/or the mucous membranes, in particular for the care,cleansing and/or application of make-up to and/or protection, from the sun, of the skin, the hair and/or the lips or the mucous membranes. It may be used, for example, as products for cleansing or removing make-up from the face (including the eyes andthe lips) or the body, as care products for the face, for example for treating the signs of ageing or for moisturizing or nourishing the skin, as antisun products for protecting the skin or the hair from UV radiation, as hair products.

Accordingly, the subject of the present invention is the cosmetic use of the composition as defined above, for the treatment, protection, care, removal of make-up from and/or cleansing of the skin, the lips and/or the hair, and/or the applicationof make-up to the skin and/or the lips.

The subject of the present invention is also a method for the cosmetic treatment of the skin, including the scalp, the hair and/or the lips, characterized in that a cosmetic composition as defined above is applied to the skin, the hair and/or thelips.

The following examples illustrate the invention. A.M. means therein "as active material". The quantities are indicated as a percentage by weight unless otherwise stated.

Procedure: The water, the glycerin, the surfactant and the preservatives are mixed at room temperature (about 20.degree. to 25.degree. C.). The ACUYLN 33 is added thereto and the mixture is homogenized. The pH is adjusted to 5.85 with sodiumhydroxide.

An iridescent gel of pH 5.85 is obtained. This gel has a viscosity at T0, measured using a No. 3 or 4 rotor (Rheomat RM180 at room temperature, that is to say at about 25.degree. C., at 200 s.sup.-1), of 4.8 poises (0.48 Pa.s).

COMPARATIVE EXAMPLE 1

ACUYLN 33 is replaced, in Example 1, with an equivalent quantity of SYNTHALEN W2000 (3V SA) (5% by weight of A.M.).

An iridescent gel of pH 5.76 is obtained. This gel has a viscosity at T0, measured using a No. 3 or 4 rotor (Rheomat RM180 at room temperature, that is to say at about 25.degree. C., at 200 s.sup.-1), of 2.5 poises (0.25 Pa.s).

COMPARATIVE EXAMPLE 2

ACUYLN 33 is replaced, in Example 2, with an equivalent quantity of SYNTHALEN W2000 (3V SA) (5% by weight of A.M.).

An iridescent translucent gel of pH 6.7 is obtained. This gel has a viscosity at T0, measured using a No. 3 or 4 rotor (Rheomat RM180 at room temperature, that is to say at about 25.degree. C., at 200 s.sup.-1), of 6 poises (0.6 Pa.s), and ithas a conductance, measured using the type CD78 conductimeter from TACUSSEL at 25.degree. C. of 6075 .mu..OMEGA..sup.-1.

COMPARATIVE EXAMPLE 3

ACULYN 33 is replaced, in Example 3, with an equivalent quantity of an aqueous dispersion of silica, that is the product marketed by the company Ikeda under the name Opalesque 1015, a 15% dispersion in water of silica particles having a size ofabout 100 nm, that is the product marketed by the company Ikeda under the name Opalesque 1030, a 30% dispersion in water of silica particles having a size of about 100 nm.

An iridescent translucent gel of pH 6 is obtained whose colours vary from blue, green, yellow, to orange depending on the orientation. This gel has a viscosity, after 10 minutes, measured with a No. 3 or 4 rotor (Rheomat RM180 at roomtemperature, that is to say at about 25.degree. C., at 200 s.sup.-1), of 15 poises (1.5 Pa.s).

An iridescent milky fluid gel of pH 7.5 is obtained whose colours vary from blue to green depending on the orientation. This gel has a viscosity, after 10 minutes, measured with a No. 3 or 4 rotor (Rheomat RM180 at room temperature, that is tosay at about 25.degree. C., at 200 s.sup.-1), of 4 poises (0.4 Pa.s).

An iridescent translucent gel of pH 6 is obtained whose colours vary from blue, green, yellow, to orange depending on the orientation. This gel has a viscosity, after 10 minutes, measured with a No. 3 or 4 rotor (Rheomat RM180 at roomtemperature, that is to say at about 25.degree. C., at 200 s.sup.-1), of 15 poises (1.5 Pa.s).